We now need to separate the following types of classes:
- Indexers (e.g. classical, singlepass, hadoop) should not be the "indexing" package. Classes relating to each should have specific packages.
- Compression classes (bit, or integer/byte) should have separate sub-packages under compression.
- Index structure classes and posting iterator that are specific to a particular compression implements (bit vs integer) should also be separated into sub-packages.